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Class 12 Integrals · Short Answer2 Marksdefinite_integration

Class 12 Maths · Integrals · Short Answer #52

Evaluate \(\int_{-\pi/4}^0(1+\tan x)/(1-\tan x)dx\).

✅ Step-by-Step Solution

Final Answer: (ln2)/2
  1. The tangent addition identity gives (1+tan x)/(1−tan x)=tan(π/4+x).
  2. The primitive is −ln|cos(π/4+x)|. Its endpoint difference is −ln(1/√2)+ln1=(ln2)/2.
  3. Therefore the integral equals (ln2)/2.

📋 CBSE Stepwise Marking Scheme

  • [0.5 marks] The tangent addition identity gives (1+tan x)/(1−tan x)=tan(π/4+x).
  • [1 mark] The primitive is −ln|cos(π/4+x)|. Its endpoint difference is −ln(1/√2)+ln1=(ln2)/2.
  • [0.5 marks] Therefore the integral equals (ln2)/2.

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